I told her there were two separate locks intertwined.

‘Anyhow this is the mother’s hair,’ she repeated. ‘That’s exactly the right colour.’

Another occasion missed when I could have proven her findings – I should have asked her to specify the hair colour before she saw the hair.

She spread the letter out on her desk. ‘The writing is from someone very disturbed,’ she repeated. She shook her head. ‘Before reading it, I would say it’s the writing of someone really disturbed. One would say someone who wants to die.’

She glanced at the first sheet. ‘It’s very long,’ she commented, discouraged by the density of the writing and the number of pages. ‘Why don’t you summarize it for me.’

‘Well,’ I began. ‘Her son died, at the dawn of summer . . .’

‘I have such a terrible headache when I hold this letter,’ the clairvoyant interrupted me. ‘There is a madness in this woman. Does the letter seem coherent to you?’

‘Given that she has lost her son . . .’ I prevaricated.

‘Yes, I see what you mean. Go on,’ she encouraged me.

I skimmed through some of the more striking phrases. ‘My life started when he was born . . . he slipped away from life . . . Forgive me for being so angry at your disappearance . . . I think there’s been some mistake . . .’ I told her about the last line, that the mother would show the letter only to one friend.

‘My impression is of a woman who is losing her reason.’ She broke off again: ‘I have such an incredibly violent pain in the head. I have to put the letter away.’

She began to cram it back into the bottle desperately. Others – the graphologist, my friend the dog-walker, the forensic detective, myself – treated the letter more like a holy relic, an important piece of precious evidence, rolling up the sheets immaculately. The clairvoyant was in a hurry to get rid of it. Like a genie, it would not go back in without a struggle. ‘It’s hurting me . . .’ she cried, so I took the letter from her and rolled it properly and tried to reinsert it into the bottle. It took a few attempts, as I was distracted by her distress and in my haste failed to roll it tightly enough. At last I managed to slide it through the narrow neck and put the top back on.

‘Good,’ she sighed in relief. She continued. ‘Perhaps the child committed suicide? I see him in the water, I see someone trying to fish out something from the water, someone diving down to the bottom of the water. I think it is a woman. I see a boat, I see a coast, so I think it was thrown in from France, towards Brittany, somewhere like that, perhaps.